KEYENCE SR-750 Series - Manual (Page 26)

26 E SR-750 UM
4-1
Reading Operations
This section describes the reading conditions of the SR-750 Series.
Steps of Read Operation
The SR-750 Series follow the read sequence below:
(1) Trigger input processing : Trigger input is verified and light is
controlled.
(2) Scanning + image transfer : The image is scanned within the specified
exposure time and the image is transferred.
(3) Decoding processing : The captured image is filtered and the code
is processed (decoded).
(4) Data communication processing : The decoded results are output as data.
Since (2) and (3) above are based on the settings registered with the parameter
banks, operation is repeated using alternate banks until a code is read or the
trigger input is turned off.
Specify the following operations for the above processing:
• Timing Mode
Specify from level trigger or one-shot trigger.
• Data Transmission Select "Send after read" or "Send after timing OFF".
• Read mode
Specify from Single, Multi1, Multi 2 or burst.
Timing Chart
This section describes the steps of basic operations of the SR-750 Series.
Operating conditions are as follows:
• Timing Mode
: Level trigger
• Timing to send data : Send after read
• Read mode
: Single
• Parameter bank : Set 2 banks, alternate mode
A: Input time constant + Scan delay time
B: Exposure time set for each parameter bank (max. 9.99 ms)
C: Image transfer time (approx. 16 ms)
D: Decode time out period set for each parameter bank (Max. 2550 ms)
F: Decoding time when reading is successful
• The above is the image when reading is successful. For read error, B, C and D
are repeated continuously and read error data is output when the trigger input is
turned off.
Scan delay time
When the entry timing of the target to be conveyed is shifted from the input timing
of the timing sensor, set the "scan delay time".
This makes it possible to start scanning under optimum read conditions by setting
the delay for the timing at which emission of light of the SR-750 begins.
• The time can be set between 0 and 255 ms in increments of 1 ms (Default: 0 ms).
• Set the scan delay period for the parameter bank.
A B B
D
C C
F
(1) Trigger input
(2) Scanning +
image transfer
(3) Decoding
processing
(4) Data
communication
Operation of parameter bank 1 Operation of parameter bank 2
Read data
Trigger input
Scanning
Input time
constant Scan delay
time
Internal bank retry count
When the internal bank retry count is set, 1 parameter bank is repeated. When
decoding cannot be complete within the specified internal bank retry count,
operation to switch to the next parameter bank is possible.
If reading operation becomes unstable due to vibration of the workpiece, setting
the internal bank retry count enables stable reading.
„ Timing Chart
• The internal bank retry count can be set within the range from 0 to 32. (Factory
setting: 0)
• If a large number is set for the internal bank retry count and multiple parameter
banks are registered, reading time per time will become longer. Secure sufficient
reading time so that reading can be stable.
4-2
Timing Mode
This section describes the timing mode of the SR-750 Series.
Type of timing mode
The SR-750 Series provides the following 2 types of timing mode.
• Level trigger
• One-shot trigger
For the remainder of this section, assume the following settings are used:
• Read mode
: Single
• Data Transmission : Send after read
• Output terminal settings OUT1 = OK
OUT2 = NG + ERROR
OUT3 = TRG BUSY
* Output terminal settings "3-6 Multi-I/O Function (Page 14)"
* For convenience sake, the timing chart does not indicate the input pulse width +
scan delay time.
Level trigger
When the trigger input turns on, the SR-750 Series turns on the illumination to start
scanning.
When a code is read successfully, it stops illumination and sends the data.
If the SR-750 Series fails to read a code, it stops illumination when the trigger input
turns off and sends a reading error.
„ Timing Chart
• Set the trigger input so it stays ON from the reading start time until reading end
time.
• The illumination of the SR-750 Series turns on after the trigger input has been
activated for the specified input time constant.
• The input time constant for the trigger input can be changed to 1 ms, 2 ms, or 10
ms.
• The RS-232C data communication time can be obtained using the following
equation:
Data communication time= × (Number of digits of data to be sent +
Number of characters of header and terminator)
• The ON time for the OK/NG/ERROR output can be set within the range of 10 to
2550 ms (Default: 500 ms).
(1) Trigger input
(2) Parameter bank 1
operation
Internal bank retry
count = a
(3) Parameter bank 2
operation
Internal bank retry
count = b
Scanning +
decoding
0 times 1 time 2 times a times
0 times 1 time b times
Scanning +
decoding
Scanning +
decoding
Scanning +
decoding
Scanning +
decoding
Scanning +
decoding
OK/NG ERROR
Trigger input
Code
Scanning + decoding
Data communication
TRG BUSY output
(When reading is successful) (When reading failed)
OK/NG/ERROR output
Data length + (1: When parity is used) + Start/stop bits
Baud rate